JPH02232556A - Formation of gas detection electrode for co2 sensor - Google Patents
Formation of gas detection electrode for co2 sensorInfo
- Publication number
- JPH02232556A JPH02232556A JP1054723A JP5472389A JPH02232556A JP H02232556 A JPH02232556 A JP H02232556A JP 1054723 A JP1054723 A JP 1054723A JP 5472389 A JP5472389 A JP 5472389A JP H02232556 A JPH02232556 A JP H02232556A
- Authority
- JP
- Japan
- Prior art keywords
- gas
- sensor
- detection electrode
- gas detection
- solid electrolyte
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000001514 detection method Methods 0.000 title claims abstract description 20
- 230000015572 biosynthetic process Effects 0.000 title 1
- 239000007784 solid electrolyte Substances 0.000 claims abstract description 18
- 239000007772 electrode material Substances 0.000 claims abstract description 10
- 239000000843 powder Substances 0.000 claims abstract description 10
- 239000002184 metal Substances 0.000 claims abstract description 7
- 229910052751 metal Inorganic materials 0.000 claims abstract description 7
- 239000000919 ceramic Substances 0.000 claims 2
- 229910001413 alkali metal ion Inorganic materials 0.000 claims 1
- 239000010931 gold Substances 0.000 abstract description 20
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 abstract description 8
- 239000011230 binding agent Substances 0.000 abstract description 5
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 abstract description 4
- 229910000029 sodium carbonate Inorganic materials 0.000 abstract description 4
- 235000017550 sodium carbonate Nutrition 0.000 abstract description 4
- 229910052737 gold Inorganic materials 0.000 abstract description 3
- 239000002270 dispersing agent Substances 0.000 abstract description 2
- 239000002003 electrode paste Substances 0.000 abstract description 2
- 239000004034 viscosity adjusting agent Substances 0.000 abstract description 2
- 239000000463 material Substances 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 32
- 230000007423 decrease Effects 0.000 description 6
- 230000002123 temporal effect Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000000855 fermentation Methods 0.000 description 1
- 230000004151 fermentation Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 1
- 244000144972 livestock Species 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Landscapes
- Measuring Oxygen Concentration In Cells (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は，固体ＴＬＭ．質を用いた空気中のＣＯよガス
濃度を測定するためのＣＯ■ガスセンサの電極の形成方
法に関する．本発明のＣＯ２ガスセンサは、環境制御，
農畜産，ｉｌｌＩｉ酵工業プロセスを始めとする多数の
分野のＣＯ■ガス濃度測定、あるいはＣＯｔ濃度制御に
使用することができる．［従来の技術］
固体電解質を用いたＣ０２センサの原理は既に公知（丸
山Ｓ：第１０回固体イオニクス討論会講演要旨集６９．
１９８３）であり、その構成は，Ｇｏ，，ｏｓ Ａｕ
Ｉ Ｎａｘｃｏａ ｌ ｌ固体電解質ｌＡｕ，Ｏ・・・
・・・・・・・・・・ （１）で示される，この時のこ
のセンサの起電力は，？＝Ｅｏ− （ＲＴ／２Ｆ）Ｉ
ｎ （ ａＮａ，Ｏ ・Ｐｃｏｚ／ ａＮａ，Ｃ○，）
ここでＥ０は定数，Ｒは気体定数．Ｔは絶対温度，Ｆは
ファラデ一定数，ａＮａ，ＯはＮ ａ，Ｏの活量，ａＮ
ａ．，Ｇｏ．はＮａ２ＣＯ３の活量． ｐｃｏ２はｃｏ
２ガス分圧である＊ ａ Ｎ ａ ｚ Ｃ Ｏ ３は通
常１と考えられ，従ってＴが一定の条件では起電力はＰ
ｃｏｔのみの関数となり，従って起電力よりＣＯ■ガ
ス濃度（分圧）を求めることができる．
従来の技術として，以下のガス検知電極構成を有するｃ
ｏ．センサが提唱されている．（１）ｆｌ！極反応を円
滑に進め、安定した起電力を得るためにＮａ，ＣＯ３を
含浸した多孔質電極をガス検知ｇ１極として用いる．
（２）Ｎａ，ＣＯ３とｆ！！極材料であるＡｕペースト
を混合，塗布し，空気中で焼成し，ガス検知電極とする
．
しかしながら、上記のいずれの場合も長期安定性という
面では問題があり、比較的短期間で起電力，感度共に大
きく低下することが明らかとなり，長期間に渡り安定に
作動するＣＯ２センサが望まれている．
［発明が解決しようとする問題点コ
上記したように、従来のＣＯ２センサは比較的短期間に
起電力、感度が共に低下するという問題点があり，これ
が本発明が解決しようとする問題点である．
［問題を解決するための手段］
本発明は，上記のような事情に鑑みてなされたものであ
る．その手段とするところは、以下に記述する３項目で
ある。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state TLM. This paper relates to a method of forming an electrode for a CO2 gas sensor for measuring the concentration of CO2 gas in the air. The CO2 gas sensor of the present invention provides environmental control,
It can be used for CO2 gas concentration measurement or COt concentration control in many fields including agriculture and livestock production and illIi fermentation industrial processes. [Prior art] The principle of a CO2 sensor using a solid electrolyte is already known (S. Maruyama: Abstracts of the 10th Solid State Ionics Symposium, 69.
1983), whose structure is Go,,os Au
I Naxcoa l l Solid electrolyte l Au, O...
What is the electromotive force of this sensor at this time, shown in (1)? =Eo- (RT/2F)I
n (aNa,O ・Pcoz/aNa,C○,) where E0 is a constant and R is a gas constant. T is absolute temperature, F is Faraday constant, aNa, O is activity of Na, O, aN
a. , Go. is the activity of Na2CO3. pco2 is co
The partial pressure of the two gases * a N a z C O 3 is usually considered to be 1, so under the condition that T is constant, the electromotive force is P
It is a function only of cot, so the CO■ gas concentration (partial pressure) can be determined from the electromotive force. As a conventional technology, c has the following gas detection electrode configuration.
o. A sensor has been proposed. (1)fl! A porous electrode impregnated with Na and CO3 is used as the gas detection g1 electrode to facilitate the polar reaction and obtain a stable electromotive force. (2) Na, CO3 and f! ! The electrode material, Au paste, is mixed, applied, and fired in air to form a gas detection electrode. However, in all of the above cases, there is a problem in terms of long-term stability, and it has become clear that both electromotive force and sensitivity decrease significantly in a relatively short period of time.Therefore, a CO2 sensor that operates stably over a long period of time is desired. There is. [Problems to be Solved by the Invention] As mentioned above, conventional CO2 sensors have the problem that both the electromotive force and the sensitivity decrease in a relatively short period of time, and this is the problem to be solved by the present invention. be. [Means for solving the problem] The present invention has been made in view of the above circumstances. The means for this are the three items described below.
（１）電極材料としてＡｕ金灰を用いＮａ２ＣＯ３を重
量％で５０％以下の割合で混合して４００℃以上９５０
℃以下の高温のｃｏ２ガス雰囲気、もしくはＣＯ２ガス
を含む雰囲気中において固体電解質上に焼き付け、ＣＯ
２ガス検知電極を形成する．
（２）電極材料としてＡｕ金属を使いＮａ２ＣＯ，を重
量％で５０％以下、固体電解質微粉末を３０％以下の範
囲で混合したＣ０２ガス検知極材料を，？００℃以上９
５０℃以下の高温のＣＯ■ガス雰囲気，もしくはＣＯ２
ガスを含む雰囲気において固体電解買上に焼き付け、Ｃ
Ｏ■ガス検知電極を形成する．
（３）？！極材料としてＡｕ金属を用いＮａオＣＯ３を
重量％で５０％以下、８５０℃以下の温度においてＡｕ
，Ｎａ，Ｃ○，，固体電解質と化合物を形成しないセラ
ミック微粉末を重量％で３０％以下の範囲で混合した検
知極構成材料を，４００℃以上９５０℃以下の高温のＣ
Ｏ■ガス雰囲気，もしくはＣＯ■ガスを含む雰囲気にお
いて固体電解質上に焼き付け，ＣＯ■ガス検知電極を形
成する．また、これらのセンサの電極材料としてのＡｕ
金３は、通常、金の微粉末と有機性分散剤，有機系結着
剤及び有機系の粘度調整剤よりなる市販のＡｕペースト
が用いられる．本発明の実施はＡｕペーストを固体電解
質上に塗布し，乾燥後Ｃ０８ガス雰囲気，あるいはＣＯ
■を含む雰囲気中で焼成することにより行なわれるが、
Ａｕ微粉末と他のガス検知極材料及び有機バインダーを
混合して調整した電極ペーストを使用しても良レ為．［
作用］
第１図にＣＯオセンサの感ガス素子概念図を示す．固体
電解質板上（１）の片面に基準電極（２）として多孔￥
ＩＡｕｆ！極が設けてあり，相対する面にＣへガス検知
電極（３）が本発明の方法によって形成されている．こ
のＣＯ２感ガス素子を第２図に示すとおり平板状ヒータ
ー（５）と接着し，ステム（７）に取り付けてＣＯ２セ
ンサとする．第１図、第２図に示すＣ○２センサを素子
温度５００℃で作動させ，ＣＯ２センサの起電力（以後
ＥＭＦと記す）及びＣＯ，ガス濃度を５００ｐｐｍから
５０００ｐｐｍに変化させた際の起電力変化量（以後Δ
ＥＭＦと記す）の経時特性を長期間に渡って測定した．
その結果として，ＥＭＦの経時特性を第３図に、ΔＥＭ
Ｆの経時特性を第４図に示す．また、本発明の処理を施
していない従来のＣＯ２センサと比較するため，従来品
のデータも合わせて示した．
第３図及び第４図中の（ａ）は、従来の多孔質？ｕｇ極
にＮａ２ＣＯ３を含浸させたガス検知極を有するＣＯ■
センサの経時特性である．又、（ｂ）は、Ａｕ粉末とＮ
ａ，Ｇｏ，粉末の混合物を固体電解質上に焼き付けて形
成したガス検知極を有するＣＯ２センサの経時特性であ
る。（２）ＣＯＣ）は、本発明の処理を施したＣＯよセ
ンサの経時特性である．第３図より．ＥＭＦは（ａ）の
ＣＯ■センサにおいては１０日目より会、激に低下し、
（ｂ）のＣＯ■センサにおいては２０日目より急激に低
下している．更に急激な低下が生じる時点までにおいて
もＥＭＦが徐々に低下していることが観察される．しか
し，本発明の処理を施したＣＯよセンサは、第３図（Ｃ
）に見られる様に、ほぼ初期のＥＭＦの値を５０日間維
持している．現時点では５０日までのデータしかないが
、更にこの特性を維持できる可能性がある．
次に第４図よりΔＥＭＦの経時特性を比較すると．ＥＭ
Ｆの経時特性と同様な傾向を示している．以上の結果よ
り，本発明の処理を施したＣＯ，センサのＥＭＦ及びΔ
ＥＭＦの経時特性は大幅に改浮されていることが確認で
きる。（２）ＣＯａ）（ｂ）（ｃ）のＣＯ２センサを単
純には比較できないが、急激にＥＭＦ及びΔＥＭＦが低
下した点を寿命とすると，本発明の処理を施すことによ
り寿命が少なくとも２．５倍、ないしは５倍以上に伸ば
すことが可能となった．
〔実施例］
ガス検出電極用ペーストはＡｕペーストを１．０ｇ、固
体電解質の微粉末（４００メッシュ以下）とＮａ２ＣＯ
，（４００メッシュ以下）をそれぞれ０．０４ｇ，０．
２７ｇ，更に有機バインダーを２０μｌ、メノウ乳鉢に
て混合し、得た。(1) Using Au gold ash as an electrode material and mixing Na2CO3 at a ratio of 50% or less by weight,
Baked onto a solid electrolyte in a high-temperature CO2 gas atmosphere below ℃ or in an atmosphere containing CO2 gas, CO
2. Form the gas detection electrode. (2) A CO2 gas sensing electrode material that uses Au metal as an electrode material and mixes Na2CO in a weight percentage of 50% or less and solid electrolyte fine powder in a range of 30% or less. 00℃ or higher9
High temperature CO gas atmosphere below 50℃ or CO2
Baked on solid electrolyte in atmosphere containing gas, C
O ■ Form a gas detection electrode. (3)? ! Au metal is used as the electrode material, NaOCO3 is 50% by weight or less, and Au is used at a temperature of 850°C or less.
C
It is baked onto a solid electrolyte in an O■ gas atmosphere or an atmosphere containing CO■ gas to form a CO■ gas sensing electrode. In addition, Au as the electrode material of these sensors
As gold 3, a commercially available Au paste consisting of fine gold powder, an organic dispersant, an organic binder, and an organic viscosity modifier is usually used. In the implementation of the present invention, Au paste is applied onto a solid electrolyte, and after drying, it is placed in a CO8 gas atmosphere or a CO2 gas atmosphere.
This is done by firing in an atmosphere containing
Even if an electrode paste prepared by mixing Au fine powder, other gas detection electrode materials, and an organic binder was used, good results were obtained. [
Function] Figure 1 shows a conceptual diagram of the gas-sensitive element of the CO sensor. A porous hole is placed on one side of the solid electrolyte plate (1) as a reference electrode (2).
IAuf! A gas detection electrode (3) is formed on the opposing surface by the method of the present invention. As shown in Figure 2, this CO2 gas sensing element is glued to a flat heater (5) and attached to the stem (7) to form a CO2 sensor. The C○2 sensor shown in Figures 1 and 2 is operated at an element temperature of 500°C, and the electromotive force (hereinafter referred to as EMF) of the CO2 sensor and the electromotive force when the CO and gas concentration are changed from 500 ppm to 5000 ppm. Amount of change (hereinafter Δ
The temporal characteristics of EMF (hereinafter referred to as EMF) were measured over a long period of time.
As a result, the EMF characteristics over time are shown in Figure 3, and ΔEM
Figure 4 shows the temporal characteristics of F. In addition, data for the conventional product is also shown for comparison with a conventional CO2 sensor that has not undergone the treatment of the present invention. Is (a) in Figures 3 and 4 the conventional porous type? CO■ with a gas detection electrode in which the ug electrode is impregnated with Na2CO3
These are the characteristics of the sensor over time. In addition, (b) shows Au powder and N
This is the aging characteristic of a CO2 sensor having a gas detection electrode formed by baking a mixture of a, Go, and powder onto a solid electrolyte. (2) COC) is the temporal characteristic of the CO sensor treated according to the present invention. From Figure 3. The EMF in the CO sensor in (a) decreased sharply from the 10th day.
The CO■ sensor in (b) shows a sharp decline from the 20th day. It is observed that the EMF gradually decreases even up to the point where a more rapid decrease occurs. However, the CO sensor treated according to the present invention is shown in Fig. 3 (C
), the initial EMF value was maintained for 50 days. At present, we only have data up to 50 days, but there is a possibility that this characteristic can be maintained even further. Next, let's compare the temporal characteristics of ΔEMF from Figure 4. E.M.
It shows a similar trend to the temporal characteristics of F. From the above results, the EMF and Δ
It can be confirmed that the EMF characteristics over time have been significantly improved. (2) COa) It is not possible to simply compare the CO2 sensors in (b) and (c), but if the life is defined as the point at which EMF and ΔEMF suddenly decrease, then by applying the treatment of the present invention, the life will be at least 2.5 It is now possible to increase the size by 5 times or more than 5 times. [Example] The paste for gas detection electrode is made of 1.0g of Au paste, solid electrolyte fine powder (400 mesh or less) and Na2CO.
, (400 mesh or less), 0.04g and 0.04g, respectively.
27 g and 20 μl of an organic binder were mixed in an agate mortar to obtain.
上記ペーストを固体電解質に塗布し、１２０℃で１０分
間乾燥させた後，ＣＯ，雰囲気中において７００℃で１
０分間焼成した。このようにして製作した素子をヒータ
ー（５）に接着し、ヒーター温度をモニターするため熱
な対（６）を付け，ステム（７）に固定した．このよう
゜にして構成したＣＯ．ガスセンサを５００℃に加熱し
，長期間に渡ってＥＭＦ及びΔＥＭＦ （ＣＯ．濃度５
００？ｐｍ−５０００ｐｐｍでのＥＭＦ変化量）を測定
した．その結果を第３図，第４図に示す．第３図はセン
サのＥＭＦの長期間に渡る経時変化状況を示したもので
ある。The above paste was applied to a solid electrolyte, dried at 120°C for 10 minutes, and then heated at 700°C for 1 hour in a CO atmosphere.
Baked for 0 minutes. The element thus produced was glued to the heater (5), a thermal couple (6) was attached to monitor the heater temperature, and it was fixed to the stem (7). The CO. configured in this manner. The gas sensor is heated to 500℃ and the EMF and ΔEMF (CO. concentration 5
00? The amount of EMF change at pm-5000 ppm) was measured. The results are shown in Figures 3 and 4. FIG. 3 shows how the EMF of the sensor changes over a long period of time.
第４図はΔＥＭＦの経時変化状況を示したものである．
［本発明の効果］
本発明の処理を施したＣＯ２センサは、睨時点において
少なくとも５０日間はＥＭＦ及び△ＥＭＦともに経時変
化をほとんど生じないことが判明した．尚、更に長期間
に渡ってこの性能を維持することが期待できる．
このことより、従来のＣＯ■センサと比較して、少なく
とも２．５倍ないし５倍以上の長寿命化を実現し，より
信頼性を向上させることに成功した．以上のことは．Ｃ
Ｏ２センサの工業的な実用化において非常に有意義であ
る．Figure 4 shows the change in ΔEMF over time. [Effects of the Present Invention] It was found that the CO2 sensor subjected to the treatment of the present invention showed almost no change over time in both EMF and ΔEMF for at least 50 days at the time of use. Furthermore, it is expected that this performance will be maintained for an even longer period of time. As a result, we have succeeded in achieving a lifespan of at least 2.5 to 5 times longer than conventional CO2 sensors and further improving reliability. That's all. C
This is very significant in the industrial practical application of O2 sensors.
第１図はＣ０２センサ素子の概念図である．第２図はＣ
Ｏ２センサの概念図である．第３図はセンサ起電力の長
期特性である．第４図はセンサ変化量の長期特性である
．（１）・・・固体電解質チップ
（２）・・・基準電極
（３）・・・ガス検知電極
（４）・ ・ ・Ａｕリード線
（５）・・・ヒーター
（６）・・・熱雷対
（７）・・・ステムFigure 1 is a conceptual diagram of the C02 sensor element. Figure 2 is C
This is a conceptual diagram of an O2 sensor. Figure 3 shows the long-term characteristics of the sensor electromotive force. Figure 4 shows the long-term characteristics of sensor variation. (1)...Solid electrolyte chip (2)...Reference electrode (3)...Gas detection electrode (4)...Au lead wire (5)...Heater (6)...Heat lightning Pair (7)...Stem
Claims (4)
体電解質という）を用いたＣＯ＿２センサにおいてＣＯ
＿２ガス検知電極を４００℃以上９５０℃以下のＣＯ＿
２ガス雰囲気もしくはＣＯ＿２ガスを含む雰囲気中で形
成することを特徴とするＣＯ＿２センサ。(1) CO_2 sensor using an alkali metal ion conductive solid electrolyte (hereinafter referred to as solid electrolyte)
_2 Gas detection electrode with CO at 400°C or higher and 950°C or lower
A CO_2 sensor characterized by being formed in a two-gas atmosphere or an atmosphere containing CO_2 gas.
あるＮａ＿２ＣＯ＿３よりなり、Ｎａ＿２ＣＯ＿３が重
量％で５０％以下であることを特徴とする特許請求の範
囲第１項記載のＣＯ＿２センサ。(2) The CO_2 sensor according to claim 1, wherein the CO_2 gas detection electrode is made of Au metal and Na_2CO_3 as a detection electrode material, and the content of Na_2CO_3 is 50% or less by weight.
＿３及びこれらとは非反応性である耐熱セラミック微粉
末よりなり、Ｎａ＿２ＣＯ＿３が重量％で５０％以下、
且つ耐熱セラミック微粉末が重量％で３０％以下の範囲
内であることを特徴とする特許請求の範囲第１項記載の
ＣＯ＿２センサ。(3) CO_2 gas detection electrode is Au metal, Na_2CO
_3 and these are made of non-reactive heat-resistant ceramic fine powder, Na_2CO_3 is 50% or less by weight,
The CO_2 sensor according to claim 1, wherein the heat-resistant ceramic fine powder is in a range of 30% or less by weight.
＿３及び固体電解質微粉末よりなり、Ｎａ＿２ＣＯ＿３
が重量％で５０％以下且つ固体電解質が重量％で３０％
以下の範囲内であることを特徴とする特許請求の範囲第
１項記載のＣＯ＿２センサ。(4) CO_2 gas detection electrode is Au metal, Na_2CO
_3 and solid electrolyte fine powder, Na_2CO_3
is 50% or less by weight, and the solid electrolyte is 30% by weight.
The CO_2 sensor according to claim 1, characterized in that the CO_2 sensor is within the following range.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1054723A JPH02232556A (en) | 1989-03-06 | 1989-03-06 | Formation of gas detection electrode for co2 sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1054723A JPH02232556A (en) | 1989-03-06 | 1989-03-06 | Formation of gas detection electrode for co2 sensor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02232556A true JPH02232556A (en) | 1990-09-14 |
Family
ID=12978721
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1054723A Pending JPH02232556A (en) | 1989-03-06 | 1989-03-06 | Formation of gas detection electrode for co2 sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02232556A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5261596A (en) * | 1991-06-14 | 1993-11-16 | Matsushita Electric Industrial Co., Ltd. | Air quality conditioning system |
-
1989
- 1989-03-06 JP JP1054723A patent/JPH02232556A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5261596A (en) * | 1991-06-14 | 1993-11-16 | Matsushita Electric Industrial Co., Ltd. | Air quality conditioning system |
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